First, using the lower left circle, by running a horizontal line from the extended arc out to the modul bar.

Second, my preferred method. These drawings are scaled to the included module key. Set a pair of dividers to the radius of the circle directly on the drawing and test that divider setting on the module key. You should read 1 module.

I used 72mm as my module, but you can substitute any reasonable distance and the drawing still works the same. For instance. You may want a stool that is 16″ from the floor to the bottom of the base. Since this distance is 4 modules on the drawing, your new distance for 1 module is 4″. You could then lay out the entire stool with two pair of dividers. One pair set at 4″ (1 module) and one pair set at 2″ (1/2 module). Simply step off all of the indicated distances per the drawing with your new module settings.